#define  _CRT_SECURE_NO_WARNINGS
class Solution {
public:
    char dismantlingAction(string arr) {
        unordered_map<int, int> um;
        for (auto e : arr)
            um[e]++;
        for (auto e : arr)
            if (um[e] == 1)
                return e;
        return ' ';
    }
};

class Solution {
public:
    char dismantlingAction(string arr) {
        int hash[128]{0};
        for (auto e : arr)
            hash[e]++;
        for (auto e : arr)
            if (hash[e] == 1)
                return e;
        return ' ';
    }
};